Preheat the oven to 200 F (95 C). This is to keep the already made ebelskivers warm while you cook the others.
Combine flour, sugar, baking powder, salt, and orange zest in a large bowl.
In a small bowl, lightly beat the egg yolks then mix in the milk, orange juice, and melted butter.
Mix the wet ingredients with the dry ingredients with a wooden spoon until the mixture is homogeneous.
Beat the egg whites until stiff peaks form.
Gently fold the egg whites into the mixture using a spatula.
The mixture is ready to be used.
Heat the ebelskivers pan over medium heat.
Grease the molds with melted butter or cooking spray.
When the pan is hot, put one tablespoon (15 ml) of mixture into each mold.
Add one teaspoon (5 ml) of Nutella to the center of the mixture, then cover with one tablespoon (15 ml) of mixture.
Cook until the bottom of the ebelskivers is lightly golden and crispy, about 3-5 minutes. Use two wooden skewers to flip the ebelskivers and cook until they are lightly golden on the second side, about 3 minutes more.
Put on a plate and serve, sprinkled with powdered sugar.